WO1996034620A1

WO1996034620A1 - Restoration of progenitor cells after antiproliferative therapy treatments

Info

Publication number: WO1996034620A1
Application number: PCT/US1996/005920
Authority: WO
Inventors: Susan A. Hudak; Donna M. Rennick
Original assignee: Schering Corporation
Priority date: 1995-05-05
Filing date: 1996-05-02
Publication date: 1996-11-07
Also published as: AU5717196A

Abstract

The use of Flt3 ligand (FL) as a reagent for administration to patients suffering from slow recovery of hematopoietic cell function, and/or poor gastrointestinal mucosa integrity.

Description

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RESTORATION OF PROGENITOR CELLS AFTER ANTIPROLIFERA IVE THERAPY TREATMENTS

10

BACKGROUND OF THE INVENTION Therapeutic treatments often make use of

15 antiproliferative regimens to control quickly regenerating cells or tissues. This is often used in treatment of neoplastic diseases; including both solid and disperse cancers. Often treatment involves antiproliferative treatments, which are intended to have a preferential effect

20 on growing cells, which include the target tissues or cells. Unfortunately, the treatment also targets other relatively fast growing cells, which in an adult animal, typically include the hematopoietic cell precursors, the gut, and the skin. See, e.g., DeVita, et al. (1989) Cancer: Principles

25 and Practice of Oncology Lippincotl^* Co., Philadelphia; and Perry (ed.) Seminars in Oncology vol. 19, which presents a series of review articles.

Because of the nonspecific nature of antiproliferative treatments, typical results of such treatment include loss of

30 hematopoietic cell function, loss of gut integrity, and also skin lesions. These result, in part, from both loss of stem cells, and loss of progenitor cells in various stages of maturation. The inability to protect progenitor cells and/or to accelerate the maturation of progenitor cells causes delay

35 in recovery. This period of delayed recovery often results in a significant period of impaired function of critical systems of the organism. In many cases, this period may cause significant suffering, and may involve additional risk of additional complications, or in severe cases, prevent

40 recovery, leading to death. For this reason, the need exists for new means to minimize loss of stem or progenitor cells and/or to accelerate maturation or development of immature cells to provide needed mature cell functions.

SUMMARY OF THE INVENTION The present invention provides methods of decreasing the severity of, or minimizing the period of loss of function of desirable cells upon antiproliferative therapeutic treatments. It results from observations in which the effects of antiproliferative treatments have been significantly minimized by treatments including a mammalian Flt3 ligand (FL) .

The present invention provides a method of accelerating recovery of a patient from adverse symptoms of an antiproliferative therapeutic treatment, the method comprising the step of administering an amount of Flt3 ligand effective to accelerate such recovery. In various embodiments, the adverse symptoms will include loss of mature hematopoietic cells-and/or loss of gastrointestinal mucosal integrity; the antiproliferative therapeutic treatment will be radiation therapy; and/or chemotherapy; or the antiproliferative therapeutic treatment will result in depletion of progenitor cells, including hematopoietic and/or gastrointestinal mucosal progenitor cells. The Flt3 ligand can be a mammalian Fit3 ligand, including a mouse or primate ligand, e.g., a human ligand.

In other embodiments, the Fit3 ligand will be a recombinant Flt3 ligand; or will be administered through gene therapy; or will be administered in combination with one of G-CSF, GM-CSF, c-kit ligand, TNF-α, IL-1, IL-6, IL-7, and IL- 11, simultaneously or in succession. The dose of the Flt3 ligand will often be administered at a dose of at least about 100 ng per kg of body weight; at least about 1 μg per kg of body weight; less than about 1 mg per kg of body weight of said patient; or less than 10 mg per kg of body weight. The route of administration will sometimes be parenteral; topical; intravenous; intramuscular; intradermal; subcutaneous; or in a slow release formulation or device. Typically, the recovery will be at least 10% faster than without treatment. In another embodiment, the invention provides a composition comprising an effective combination of Flt3 ligand and G-CSF. The composition will often further comprise a pharmaceutically acceptable carrier. In various embodiments, the composition improves recovery from an antiproliferative therapeutic treatment, including radiation therapy; and/or chemotherapy.

The invention also provides a method of minimizing adverse effects on gastrointestinal mucosa integrity or mature hematopoietic cell profile from radiation therapy or chemotherapy, which comprises a step of administering an effective amount of Flt3 ligand or an effective amount of Flt3 ligand in combination with G-CSF. In one embodiment, the adverse effect is on hematopo.ietic cell depletion; in another the gastrointestinal mucosu is gut mucosa and the therapy is radiation therapy. The route of administration of Flt3 ligand may be parenteral.

DETAILED DESCRIPTION

OUTLINE

I. General

II. Production of FL III. Antiproliferative therapies

IV. Progenitor cells

V. Recovery

VI. Administration

I. General

This invention provides an effective means for increasing levels of progenitor cells when said levels are being inhibited by antiproliferative therapy, i.e., radiation or chemotherapy. Treatment of patients with antiproliferative agents has been shown to cause several physiological disorders such as depletion of hematopoietic or neural stem cells , gastrointestinal perforation and sepsis, or skin lesions.

Maintenance of the levels of stem cells and prevention of gastrointestinal.and skin lesions are important in preventing susceptibility to bacterial or viral infections, and the general discomfort to the patient undergoing the above therapy.

II. Production of Flt3 Ligand Sequences and clones encoding various mammalian Flt3 ligands have been described, e.g., in U.S.S.N. 08/261,553; 08/162,413; 08/155,111; 08/112,391; 08/106,340; 08/089,263; 08/065,231; 08/683,394; 08/106,463; 08/111,758; 08/162,407; 08/209,502; and 08/243,545. See also Hannum, et al. (1994) Nature 368:643-648; Lyman, et al. (1994) Blood 83:2795-2801; and Lyman, et al. (1993) Cell 75:1157-1167. Descriptions of vectors useful for expression are included in Pouwels, et al. (1985 and Supplements) Cloning Vectors: A Laboratory Manual, Elsevier, N.Y.; Rodriquez, et al. (1988) (eds.) Vectors: A Survey of Molecular Cloning Vector:^** and Their Uses.

Buttersworth, Boston, MA; Rodriguez and Denhardt (eds.) Vectors: A Survey of Molecular Cloning Vectors and Their Uses. Buttersworth, Boston, Chapter 10, pp. 205-236; Okayama, et al. (1985) Mol. Cell Biol. 5:1136-1142; Thomas, et al. (1987) Cell 51:503-512; Low (1989) Biochi . Biophvs. Acta 988:427-454; Tse, et al. (1985) Science 230:1003-1008; and Brunner, et al. (1991) J. Cell Biol. 114:1275-1283.

Physical variants encompass proteins or peptides having substantial amino acid sequence homology with the a ino acid sequence of a Fit3 ligand. Techniques for producing such variants can be found in U.S.S.N. 08/261,553; 08/162,413; 08/155,111; 08/112,391; 08/106,340; 08/089,263; 08/065,231; 08/683,394; 08/106,463; 08/111,758; 08/162,407; 08/209,502; and 08/243,545. Descriptions of how comparisons are made are found, e.g., in Needleham, et al. (1970) J. Mol. Biol.

48:443-453; Sankoff, et al. (1983) Chapter One in Time Warns. String Edits, and Macro olecules: The Theory and Practice of Sequence Comparison Addison-Wesley, Reading, MA; and software packages from IntelliGenetics, Mountain View, CA; the University of Wisconsin Genetics Computer Group, Madison, I. Methods to manipulate nucleic acids are described, e.g., in Sambrook, et al. (1989) Molecular Cloning: A Laboratory Manual (2d ed.), Vols. 1-3, Cold Spring Harbor Laboratory; Ausubel, et al., Biology. Greene Publishing Associates, Brooklyn, NY; Ausubel, et al. (1987 and Supplements) Current

Protocols in Molecular Biology. Greene/Wiley, New York;

Innis, et al. (eds.) (1990) PCR Protrocols: A Guide to Methods and Applications Academic Press, N.Y. ; Cunningham, et al. (1989) Science 243:1330-1336; O'Dowd, et al. (1988) -T. Biol.

Che . 263:15985-15992; and Beaucage and Carruthers (1981)

Tetra. Letts. 22:1859-1862.

Synthetic FL polypeptides are described, e.g., in

U.S.S.N. 08/261,553; 08/162,413; OH/155,111; 08/112,391; 08/106,340; 08/089,263; 08/065,231; 08/683,394; 08/106,463; 08/111,758; 08/162,407; 08/209,502; and 08/243,545. General descriptions of synthetic peptide synthesis are found, e.g., in Merrifield (1963) J. Amer. Chem. Soc. 85:2149-2156; Merrifield (1986) Science 232: 341-347; Atherton, et al. (1989) Solid Phase Peptide Synthesis: A Practical Approach, IRL Press, Oxford; Stewart and Young (1984) Solid Phase Peptide Synthesis. Pierce Chemical Co., Rockford, IL; Bodanszky and Bodanszky (1984) The Practice of Peptide Synthesis. Springer-Verlag, New York; and Bodanszky (1984) The Principles of Peptide Synthesis. Springer-Verlag, New York.

Recombinantly or synthetically prepared ligand and fragments thereof can be isolated and purified by peptide separation methods, e.g., by extraction, precipitation, electrophoresis, and various forms of chromatography, and the like. The Flt3 ligands of this invention can be obtained in varying degrees of purity depending upon its desired use. Purification can be accomplished by use of techniques as described in U.S.S.N. 08/261,553; 08/162,413; 08/155,111; 08/112,391; 08/106,340; 08/089,263; 08/065,231; 08/683,394; 08/106,463; 08/111,758; 08/162,407; 08/209,502; and 08/243,545. In particular, affinity chromatography will be useful, e.g., by the use of the antibodies herein described, or by use of constructs based upon the Flt3 receptor. Affinity chromatography is carried out by first linking the antibodies or receptors, e.g., to a solid support and then contacting the linked binding compositions with solubilized lysates of appropriate source cell:3, lysates of other cells expressing the ligand, or lysates or supernatants of cells producing the Flt3 ligand as a result of DNA techniques. The ligand can be gently removed from the affinity reagents.

III. Antiproliferative therapies Therapeutic treatment of highly proliterative cells has usually involved radiation therapy and/or chemotherapy as described, e.g., in.DeVita, et al. Cancer: Principle and Practice of Oncology. Lippincott Co., Philadelphia; Thorn, et al. Harrison's Principles of Internal Medicine. McGraw-Hill, N.Y.; and Weatherail, et al. (eds.) Oxford Textbook of

Medicine. Oxford University Press, Oxford. The treatment may be used for both solid tumors and disperse tumors, or other circumstances where nonspecific antiproliferative treatments are used. The treatment may be local, but will more usually be systemic treatment.

These therapies typically have detrimental effects generally upon the hematopoietic and gastrointestinal systems of the subject organism. Typically, the subject suffers from nausea, vomiting, malaise, lack of appetite, etc. Tissues which are sensitive to antiproliferative therapies include lymphoid cells, gonads, proliferating bone marrow cells, epithelial cells of^•the bowel, epidermis, hepatic cells, epithelium of the lung, kidney epithelium, and others. In particular, the loss of hematopoietic function, both myeloid and lymphoid, and gastrointestinal problems are typically most acute. See, e.g., DeVita, et al. Cancer; Principles and Practice of Oncology Lippincott Co., Philadelphia; and Perry (ed.) Seminars in Oncology October, 1992, vol. 19, which presents a series of review articles.

IV. Progenitor cells

Progenitor cells differentiate to more mature cell types by a maturation process. See, e.g., Gilbert (1991) Developmental Biology (3d ed.), Sinauer Associates, Sunderland, MA; Browder, et al. (1991) Developmental Biology (3d ed.), Saunders, Philadelphia, PA.; Russo, et al. (1992) Development: The Molecular Genetic Approach. Springer-Verlag, New York, N.Y.; and Wilkins (1993) Genetic Analysis of Animal Development (2d ed.) Wiley-Liss, New York, N.Y. In particular, there is a sequence of cell differentiation steps in the maturation of each of the cell types: hematopoietic cells, both myeloid and lymphoid, see, e.g., Paul (ed., 1994) Fundamental Immunology 3d ed. , Raven Press, New York; gastrointestinal mucosa cells, see, e.g., Yamada (1995) Atlas of Gastroenterolocry Lippincott Co., Philadelphia; and Sleisenger and Fordtran (1990) Gastrointestinal Disease: Pathophysiolocrv/ Diagnosis/ Management (4th ed.) Saunders, Philadelphia PA; skin cells, see, e.g., Fitzpatrick, et al. (eds. 1993) Dermatology in

General Medicine (4th ed.) McGraw-Hill, NY; and neural cells.

V. Recovery

Recovery from the effects of antiproliferative treatments are found in each of these cell types. Various means to assay for the effects of and recovery from treatment exist in each of the significant cell types described herein.

Among the hematopoietic cells, both myeloid and lymphoid, there are histological measures which are indicative of the health of the individual. For example, a cursory view of a blood sample can indicate whether the proportion and numbers of particular cell types are normal, e.g., red blood cells, white blood cells, B cells, T cells, NK cells, monocytes, macrophages, neutrophils, basophils, eosinophils, etc.

A number of assays have been developed to assay for the competence of particular cells, e.g., progenitors, to differentiate into more mature cell types. See, e.g., Rapaport (1987) Introduction to Hematoloσv (2d ed.) Lippincott, Philadelphia, PA; Jandl (1987) Blood: Textbook of Hematology. Little, Brown and Co., Boston, MA.; and Metcalf (1984) The Hemopoietic Colony Stimulating Factors Elsevier, Amsterdam; Metcalf (1993) Blood 82:3515-3523. There are well recognized time periods necessary for particular cell types to recover after radiation therapy and/or chemotherapy.

With regard to gastrointestinal mucosa, various measures for its health exist, See, e.g., Ogra, et al. (eds., 1994) Handbook of Mucosal Immunology Academic Press, San Diego, CA. Among other measures, histological examination can reveal the integrity of the various layers, and other measures of integrity exist, e.g., means to determine the numbers of intestinal flora who escape the gut and enter into the body. The time course for degradation and recovery of the gastrointestinal mucosa may also be evaluated.

Skin cells and related epithelial cell layers can be evaluated histologically, and biologically. In particular, the integrity of the layer may be examined for lesions, or the thickness of various cell layers may be monitored. See, e.g., Banks (1994) Applied Veterinary Histology Mosby

Yearbook Co., NY; Ross, et al. (1989) Histology: a Text and Atlas (2d ed.) Williams and Wilkins, Baltimore, MD; and DiFiore (1986) Atlas of Human Histology Philadelphia, PA; each of which is also relevant to histology of the other tissues described.

Neural cells also are affected by radiation, and the effects may be monitored histologically. See, e.g., Aldehan (ed., 1994) Encyclopedia of Neuroscience Birkhauser, Boston, MA. Other functions may be more difficult to fully evaluate, but models exist as to the rate of recovery of normal growth or physiological function exist. See, e.g., the series Methods in Neuroscience Academic Press, NY.

Recovery will normally be accelerated by at least about 10%; more normally by at least about 20%; ordinarily by at least about 30%; more ordinarily by at least about 50%; preferably by at least about 70%; more preferably by at least about 90%; and most preferably the probelms might be totally eliminated with respect to various functional losses.

VI. Administration

The FL can be purified and then administered to a patient. The reagents can be combined for therapeutic use with additional active or inert ingredients, e.g., in conventional pharmaceutically acceptable carriers or diluents, e.g., with physiologically innocuous stabilizers and excipients. These combinations can be sterile filtered and placed into dosage forms as by lyophilization in dosage vials or storage in stabilized aqueous preparations. The quantities of reagents necessary for effective therapy will depend upon many different factors, including means of administration, target site, physiological state of the patient, and other medicants administered. Thus, treatment dosages should be titrated to optimize safety and efficacy. Typically, dosages used in vitro may provide useful guidance in the amounts useful for in situ administration of these reagents. Animal testing of effective doses for treatment of particular disorders will provide further predictive indication of human dosage.

Various considerations are described, e.g., in Gilman, et al. (eds. ) (1990) Goodman and Gilman's: The Pharmacological Bases of Therapeutics. 8th Ed., Pergamon Press; and Remington's Pharmaceutical Sciences. 17th ed. (1990) , Mack Publishing Co., Easton, Penn. Methods for administration are discussed therein, e.g., for oral, intravenous, intraperitoneal, or intramuscular administration, transdermal diffusion, and others. Pharmaceutically acceptable carriers will include water, saline, buffers, and other compounds described, e.g., in the Merck Index. Merck & Co., Rahway, New Jersey. Dosage ranges would ordinarily be expected to be in amounts lower than 1 mM concentrations, typically less than about 10 μM concentrations, usually less than about 100 nM, preferably less than about 10 pM (picomolar) , and most preferably less than about 1 fM (femtomolar) , with an appropriate carrier. Slow release formulations, or a slow release apparatus will often be utilized for continuous administration. Alternatively, recombinant clones will be useful for gene therapy. See, e.g., Rosenberg (1992) __ Clinical Oncology 10:180-199.

The FL may be administered directly to the host to be treated or it may be desirable to conjugate it to carrier proteins such as ovalbumin or serum albumin prior to administration. Therapeutic formulations may be administered in many conventional dosage formulations. While it is possible for the active ingredient to be administered alone, it is preferable to present it as a pharmaceutical formulation. Formulations typically comprise at least one active ingredient, as defined above, together with one or more acceptable carriers thereof. Each carrier should be both pharmaceutically and physiologically acceptable in the sense of being compatible with the other ingredients and not injurious to the patient. Formulations include those suitable for oral, rectal, nasal, topical, or parenteral (including subcutaneous, intramuscular, intravenous and intradermal) administration. The formulations may conveniently be presented in unit dosage form and may be prepared by any methods well known in the art of pharmacy. See, e.g., Gilman, et al. (eds.) (1990) Goodman and Gilman's: The Pharmacological Bases of Therapeutics. 8th Ed., Pergamon Press; and Remington's Pharmaceutical Sciences, 17th ed. (1990), Mack Publishing Co., Easton, Penn.; Avis, et al. (eds.) (1993) Pharmaceutical Dosage Forms: Parenteral Medications Dekker, New York; Lieberman, et al. (eds.) (1990) Pharmaceutical Dosage Forms: Tablets Dekker, New York; and Lieberman, et al. (eds.) (1990) Pharmaceutical Dosage Forms: Disperse Systems Dekker, New York. The therapy of this invention may be combined with or used in association with other therapeutic agents.

In particular, the administration will likely be in combination with other aspects in a therapeutic course of treatment. In particular, the administration may involve multiple administrations, in combination with other entities, e.g., G-CSF, GM-CSF, c-kit ligand (stem cell factor), IL-1, IL-6, IL-7, and/or IL-11. The course of treatment may also involve pretreatment before antiproliferative treatment. Alternatively, the dosage may be adjusted according to a monitoring of need based, e.g., on the types of assays described above.

The broad scope of this invention is best understood with reference to the following examples, which are not intended to limit the invention to specific embodiments.

EXAMPLES

I. General Methods

Some of the standard methods are described or referenced, e.g., in Maniatis et al. (1982) Molecular Cloning. A Laboratory Manual. Cold Spring Harbor Laboratory, Cold Spring Harbor Press; Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual. (2d ed.), vols 1-3, CSH Press, NY; Ausubel et al. , Biology. Greene Publishing Associates, Brooklyn, NY; or Ausubel et al. (1987 and Supplements)

Current Protocols in Molecular Biology. Greene/Wiley, New York; Innis et al. (eds.) (1990) PCR Protocols: A Guide to Methods and Applications Academic Press, N.Y. Methods for protein purification include such methods as ammonium sulfate precipitation, column chromatography, electrophoresis, centrifugation, crystallization, and others. See, e.g., Ausubel et al. (1987 and periodic supplements); Deutscher (1990) "Guide to Protein Purification" in Methods in Enzymolocry. vol. 182, and other volumes in this series; and manufacturer's literature on use of protein purification products, e.g., Pharmacia, Piscataway, N.J., or Bio-Rad, Richmond, CA. Combination with recombinant techniques allow fusion to appropriate segments, e.g., to a FLAG sequence or an equivalent which can be fused via a protease-removable sequence. See, e.g., Hochuli (1989) Chemische Industrie 12:69-70; Hochuli (1990) "Purification of Recombinant Proteins with Metal Chelate Absorbent" in Setlow (ed.) Genetic Engineering. Principle and Methods 12:87-98, Plenum Press, N.Y.; and Crowe et al. (1992) OIAexpress: The High Level Expression _ Protein Purification System OUIAGEN. Inc., Chatsworth, CA.

FACS analyses are described in Melamed et al. (1990) Flow Cytometry and Sorting Wiley-Liss, Inc., New York, NY; Shapiro (1988) Practical Flow Cvtometrv Lisε, New York, NY; and Robinson et al. (1993) Handbook of Flow Cvtometrv Methods Wiley-Liss, New York, NY.

II. Radioprotection of Lethally Irradiated Mice

Radioprotection if irradiated mice was demonstrated using FL by endpoints of death, radiorecovery, progenitor or stem cell mobilization, and recovery of hematopoietic parameters.

Mice were lethally irradiated (1000R) , and survival of animals was determined, without treatment, with IL-1 administration (100 ng doses at periodic intervals) , and with FL administration (20 μg doses at periodic intervals) .

Without treatment, the mice started to die at about 8 days, and all died by about 13 days. Small numbers of IL-1 treated mice also started to die at about 8 days, but only about 75% died by 30 days. The FL treated mice started to die at about 13 days, and 80% were still alive at 30 days.

These mice were also analyzed at day 9 for bacterial cultures from blood and liver samples. Normal mice had no bacteria in either sample, the untreated mice all had blood and liver bacteria; while neither of the IL-1 or FL treated mice did. This suggests that the gut retained far better integrity after the radiation treatment, as bacteria had not escaped from the intestinal tract. In evaluating the bone marrow, at day 1, all irradiated mice exhibited congestion, hemorrhage, and loss of large numbers of cells. By day 5, a few mice, especially the FL treated, had clones of cells in the marrow. At day 9, IL-1 mice had greater marrow cellularities than the controls, but the FL treated mice had a clear cut greater cellularity.

In evaluating the femur populations at day 12 by a CFU-c assay, see Johnson, et al. Proc. Nat'1 Acad. Sci. USA 74:3879-3884, the FL treated mice showed greater recovery. The 20 day analysis showed even greater recovery. Different doses and times of administration might be modified to achieve an improved result for various different levels of irradiation.

III. Recovery of Sublethally Irradiated Mice Mice were sublethally irradiated at 750 R. Animals were injected twice daily for 14 days; 1 μg doses for G-CSF; 2.5 μg doses for FL; or combination at the same levels.

Analyses were performed on 4, 8, 12, 15, 20, and 26 day samples. Histological evaluation of peripheral blood cells indicated that the numbers of neutrophils increased upon treatment with either FL or FL with G-CSF. These were most pronounced at about the 12-20 day post irradiation timepoints. Hematopoietic progenitor cell analysis were performed on 7, 14, and 21 day samples. At the 14 and 21 day samples, each of G-CSF; FL; and G-CSF with FL exhibited improved bone marrow cellularities.

IV. Hematopoietic Progenitor Cell Effects

Normal mice were evaluated with respect to ability to increase numbers of hematopoietic progenitor cells released to peripheral blood. Evaluation of both white blood cell and neutrophil counts by a stem cell mobilization assay, see

Molineux, et al. Blood 76:2153- 2158, showed that FL with G- CSF synergized to improve both counts. FL itself improved the results in a CFU-s assay. Synergy was observed using a CFU-c assay, and a CFU-s assay. This suggests that FL or FL in combination with G-CSF may function to cause hematopoietic progenitor cells to be released from the originating internal organs into the blood stream, which will allow harvesting by simpler blood collection for subsequent use. This will avoid more invasive procedures for harvesting the early progenitor cells.

Many modifications and variations of this invention can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments described herein are offered by way of example only, and the invention is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

WHAT IS CLAIMED IS:

1. A method of accelerating recovery of a patient from adverse symptoms of antiproliferative therapeutic treatment comprising the step of administering an amount of Fit3 ligand, said amount effective to accelerate said recovery.

2. A method of minimizing adverse effects on gastrointestinal mucosa integrity or mature hematopoietic cell profile from radiation therapy or chemotherapy, said method comprising a step of administering an effective amount of Flt3 ligand or an effective amount of Flt3 ligand in combination with G-CSF.

3. A method for the manufacture of a pharmaceutical composition for treating a patient who has had antiproliferative therapeutic treatment comprising admixing an Flt3 ligand with a pharmaceutically acceptable carrier.

4. The method of Claims 1 to 3, wherein said Flt3 ligand is a human Flt3 ligand.

5. The method of Claims 1 to 3, wherein said Flt3 ligand is a recombinant Flt3 ligand.

6. The method of Claim 1, wherein said Flt3 ligand is administered through gene therapy.

7. The method of Claim 1 to 2, wherein said Flt3 ligand is administered in combination with one of G-CSF, GM- CSF, c-kit ligand, IL-1, IL-6, IL-7, and IL-11, simultaneously or in succession.

8. The method of Claims 1 to 2, wherein said Flt3 ligand is administered at a dose of : a) at least 100 ng per kg of body weight of said patient; b) at least 1 μg per kg of body weight of said patient; c) less than 1 mg per kg of body weight of said patient; or d) less than 10 mg per kg of body weight of said patient .

9. The method of Claim 1 to 2, wherein said administration is: a) parenteral; b) topical; c) intravenous; d) intramuscular; e) intradermal; f) subcutaneous; or g) in a slow release formulation or device.

10. A composition comprising an effective combination of Flt3 ligand and G-CSF.

11. The composition of Claim 9, further comprising a pharmaceutically acceptable carrier.

12. The use of a Flt3 ligand for accelerating recovery of a patient from adverse symptoms of antiproliferative therapeutic treatment .

13. The use of a Flt3 ligand for the manufacture of a medicament for treating a patient who has had antiproliferative therapeutic treatment.

14. A pharmaceutical composition for treating a patient who has had antiproliferative therapeutic treatment comprising Flt3 ligand and a pharmaceutically acceptable carrier.